In a similar method, known from German Pat. No. 661,901, a cylindrical, blank, seamless tube made of soft iron is cut to the appropriate length and brought to the desired cross-sectional shape by means of a hammer forge. Then this hollow body is stamped in a press with appropriate forging dies, simultaneously using a shaping mandrel, so that the hollow body, in an annealing, pressing and drifting installation, can then be brought to maximum accuracy as regards size, shape, smooth surfaces and edges.
In order to produce sharp lengthwise edges, the hollow bodies are rolled to the desired edge sharpness using an appropriate mandrel and applying fluted and curved, interchangeable profile mill cutters. After the tube has been shaped to the desired cross-sectional profile, the surface of this hollow body is given its file cut, then casehardened in a pack hardening, casehardening or nitriding process, so that the file teeth, made of soft iron, will acquire the necessary hardness.
On the one hand, this method is very costly; on the other hand, carbonized file steel is not the same as conventional file steel.
It is known from German Pat. No. 473,998 to make files from tubes, with the teeth being produced by drawing the tube through a matrix. Since the teeth run parallel to the axial direction of the tube after drawing, the tube is rotated in the warm state in order to bring the lengthwise-running teeth into the correct cutting position. Then the tube is cut in half lengthwise, and each half of the tube is bent flat again. The purpose of this method is to avoid the conventional tooth-cutting methods such as cutting or grinding and to use a simpler method of making the teeth, namely drawing.